This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-227484 filed on Jul. 27, 2000.
1. Field of the Invention
The present invention relates to a geared motor, and more specifically to a geared motor used in a power window system for moving up and down a vehicle door window glass.
2. Description of Related Art
For example, in the power window system for moving up and down the vehicle door window glass or in a power sunroof system for moving a vehicle sunroof forward and backward, a geared motor is used as a drive source. In one previously proposed geared motor, rotation of a rotatable shaft of the motor is reduced in speed by a worm wheel and is then transmitted to an output shaft. One previously proposed mechanism for transmitting the rotation of the worm wheel to the output shaft has the following structure. That is, the worm wheel is rotatably supported about and slidably engaged with a support shaft secured to a housing of the motor. A rotation transmitting member is arranged about the support shaft to oppose the worm wheel, such that the rotation transmitting member receives the rotation of the worm wheel upon engagement with projections or the like provided in an opposing end surface of the worm wheel. The rotation transmitting member is secured to an output gear that is rotatably supported about and slidably engaged with the support shaft. Furthermore, in order to reduce weight of the geared motor and also to improve assembly of the geared motor, the rotation transmitting member and the output gear are integrally formed together as an integral output shaft from a resin material.
In the above-described type of previously proposed geared motor, the size (particularly, thickness) and weight of the geared motor have been reduced, so that the geared motor can be placed within a vehicle door and a vehicle roof to operate the power window system and the sunroof system, respectively.
Furthermore, in the above-described geared motor, an O-ring is fitted around the support shaft to restrain penetration of water or the like into an interior of the housing. The O-ring is compressed in a radial direction of the support shaft between the support shaft and the output shaft (the rotation transmitting member) and is retained in place, for example, by a C-ring, so that the penetration of the water or the like into the interior of the housing through a boundary between the support shaft and the output shaft (output gear) is restrained.
In order to achieve a predetermined strength-required by an end system (load exerting side system), such as the power window system or the power sunroof system, the output gear is often required to be made of a metal material. On the other hand, a reduction in the weight of the entire geared motor has been demanded. To satisfy the demand, the rotation transmitting member can be manufactured from a resin material, and the output gear can be manufactured from the metal material. Then, the rotation transmitting member and the output gear can be insert molded together to form an integrated component (hereinafter referred to as an insert molded component).
Although this allows achievement of both the increased strength and the weight reduction of the geared motor, sealing needs to be provided between the constituents of the insert molded component. That is, in addition to the sealing between the support shaft and the output shaft (output gear) achieved with the O-ring, additional sealing needs to be provided between a connecting surface of the output gear and a corresponding connecting surface of the rotation transmitting member to be connected together.
To avoid the provision of this additional sealing, the following arrangement could be provided. That is, the rotation transmitting member can have a slidably engaging portion as an integral part thereof to be placed next to the output shaft. The slidably engaging portion of the rotation transmitting member has an inner diameter substantially the same as the inner diameter of the output gear and slidably engages the support shaft. An end surface of the slidably engaging portion of the rotation transmitting member is engaged with and is insert molded with an opposing end surface of the output shaft. In this way, the above mentioned additional sealing can be eliminated, and it is only required to provide the above mentioned O-ring that is compressed between the support shaft and the rotation transmitting member in the radial direction of the support-shaft and that is retained by the C-ring.
However, in the geared motor having the insert molded component, the output gear needs to be inserted to a predetermined depth within the rotation transmitting member to maintain the required strength of the insert molded component. Thus, the rotation transmitting member needs to have an additional thickness corresponding to the predetermined depth for inserting the output gear. In the geared motor having the rotation transmitting member provided with the slidably engaging portion to which none of the output gear and the O-ring can be inserted, since the slidably engaging portion cannot be eliminated, the thickness of the rotation transmitting member is disadvantageously increased, thereby increasing the thickness of the geared motor. Furthermore, provision of two O-rings at the above mentioned two sealing points may be possible but disadvantageously increases the number of the components and the number of the assembling steps.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a geared motor that can seal between a support shaft and an output gear and also between the output gear and a rotation transmitting member with a single seal member without substantially increasing a size of the geared motor.
To achieve the objective of the present invention, there is provided a geared motor including a housing, a support shaft, a worm wheel, a rotation transmitting member, an output gear and a seal member. The housing receives a worm connected to a rotatable shaft of the motor. The support shaft has one end secured to a base of the housing. The worm wheel is meshed with the worm within the housing. The worm wheel is rotatably supported about and slidably engaged with the support shaft. The rotation transmitting member is rotatably supported about the support shaft within the housing through a through hole axially penetrating through a center of the rotation transmitting member. The through hole of the rotation transmitting member has an inner diameter larger than an outer diameter of the support shaft. At least a portion of one end of the rotation transmitting member located around the through hole is slidably engaged with one end of the worm wheel. The rotation transmitting member is drivingly engageable with the worm wheel for receiving rotation of the worm wheel. The output gear is shaped into a generally cylindrical shape and is rotatably supported about and slidably engaged with the support shaft. One end of the output gear is secured to the other end of the rotation transmitting member such that the output gear integrally rotates with the rotation transmitting member. At least a portion of the output gear is protruding out of the housing. The seal member is fitted around the support shaft. The seal member is sealingly engaged with an outer peripheral surface of the support shaft, an inner peripheral surface of the rotation transmitting member, the one end of the worm wheel and the one end of the output gear, respectively.
In place of the above-described seal member, there can be provided a seal member placed in a seal retaining portion defined by the outer peripheral surface of the support shaft, the inner peripheral surface of the rotation transmitting member, the one end of the worm wheel and the one end of the output gear. This seal member seals between the support shaft and the output gear and also between the rotation transmitting member and the output gear, respectively.